Honorable mention:
Hyperview - Lets you use Server-Driven UI Rendering of a native app, via rendering server-generated XML. Could be used with Rails, Django or any HTTP server on the back-end etc.
"Hyperview is our open-source project to bring the benefits of thin-client, HATEOAS development to native mobile apps. The project consists of two parts:
Hyperview XML (HXML) is an XML-based format to describe native mobile UIs. It supports common UI elements like headers, scroll views, lists, text field, and much more. It also supports styling and a behavior syntax for describing user interactions (touches, gestures, input interaction) without the need for scripting.
Hyperview Client is a cross-platform library for rendering HXML in mobile apps. Implemented in React Native, it can be embedded in existing apps, or you can use it to create a new app from scratch."